Image processing device and image processing method

ABSTRACT

The present technology relates to an image processing device and an image processing method capable of reducing a used amount of a memory while suppressing deterioration in a noise reduction effect of an image. An image processing device is provided with a reduced image generation unit which reduces an original image in a stepwise manner to generate one or more n reduced images, a noise reduction unit which reduces a noise component in a predetermined frequency band of the original image, a noise extraction unit which performs processing of extracting a noise component in a predetermined frequency band from each of the reduced images in parallel, a noise synthesis unit which synthesizes noise components extracted from the respective reduced images, and a subtraction unit which subtracts a synthesized noise component from the original image after noise reduction. The present technology is applicable to, for example, an image processing device which reduces image noise.

TECHNICAL FIELD

The present technology relates to an image processing device and animage processing method, and especially relates to an image processingdevice and an image processing method suitable for use in a case ofreducing noise of an image.

BACKGROUND ART

Generally, human eyes have higher visibility for low-frequencycomponents than high-frequency components of an image. Therefore, in acase where noise of an image is reduced by using two-dimensional noisereduction (NR) with a small number of taps, low-frequency noise remainswithout being removed, and the noise is noticeable in some cases. On theother hand, if the number of taps of the NR is increased in order toreduce the low-frequency noise, a circuit scale and an arithmetic amountincrease.

Therefore, it is conventionally suggested to reduce the image in astepwise manner to reduce high-frequency noise of the reduced image ateach step (refer to, for example, Patent Document 1). Specifically, thehigh-frequency noise of the reduced image approximates the low-frequencynoise of the image before reduction. Therefore, by reducing thehigh-frequency noise from the reduced image, it is possible to obtain aneffect substantially equivalent to that in a case of reducing thelow-frequency noise of the original image. Also, since thehigh-frequency noise may be reduced by the NR with a small number oftaps, it is possible to suppress an increase in circuit scale andarithmetic amount.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-166513

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the invention disclosed in Patent Document 1, since theprocessing of the NR is sequentially performed, it is necessary thateach NR stands by for the end of the processing of a precedent NR, sothat a used amount of a memory increases.

The present technology is achieved in view of such a situation, and anobject thereof is to reduce the used amount of the memory whilesuppressing deterioration in noise reduction effect of an image.

Solutions to Problems

An image processing device according to one aspect of the presenttechnology is provided with a reduced image generation unit whichreduces an original image in a stepwise manner to generate one or more nreduced images, a noise reduction unit which reduces a noise componentin a predetermined frequency band of the original image, a noiseextraction unit which performs processing of extracting a noisecomponent in a predetermined frequency band from each of the reducedimages in parallel, a noise synthesis unit which synthesizes noisecomponents extracted from the respective reduced images, and asubtraction unit which subtracts a synthesized noise component from theoriginal image after noise reduction.

It is possible to make frequency bands of the noise components extractedfrom the respective reduced images not overlapped with a frequency bandin which the noise component is reduced by the noise reduction unit anda frequency band of the noise component extracted from another reducedimage.

It is possible to make the noise reduction unit to reduce the noisecomponent of the original image by using a filter the same as a filterused for reducing the original image and make the noise extraction unitto extract the noise component of each of the reduced images by using afilter the same as a filter used for reducing each of the reducedimages.

It is possible that the noise extraction unit is provided with nextraction units which individually extract the noise components of therespective reduced images, and it is possible to make the noisereduction unit and the n extraction units to independently performprocessing in parallel.

It is possible to make the noise synthesis unit to synthesize the noisecomponents by adding the noise components in order from the noisecomponent of the smallest reduced image while up-sampling at anenlargement factor opposite to a reduction factor when reducing thecorresponding reduced image in a case of n≥2.

An image processing method according to one aspect of the presenttechnology includes a reduced image generating step of reducing anoriginal image in a stepwise manner to generate one or more n reducedimages, a noise reducing step of reducing a noise component in apredetermined frequency band of the original image, a noise extractingstep of performing processing of extracting a noise component in apredetermined frequency band from each of the reduced images inparallel, a noise synthesizing step of synthesizing noise componentsextracted from the respective reduced images, and a subtracting step ofsubtracting a synthesized noise component from the original image afternoise reduction.

In one aspect of the present technology, an original image is reduced ina stepwise manner, one or more n reduced images are generated, a noisecomponent in a predetermined frequency band of the original image isreduced, processing of extracting a noise component in a predeterminedfrequency band from each of the reduced images is performed in parallel,noise components extracted from the respective reduced images aresynthesized, and a synthesized noise component is subtracted from theoriginal image after noise reduction.

EFFECTS OF THE INVENTION

According to one aspect of the present technology, it is possible toreduce the used amount of the memory while suppressing the deteriorationin noise reduction effect of an image.

Meanwhile, the effect is not necessarily limited to the effect hereindescribed and may be any of the effects described in the presentdisclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an embodiment of an imageprocessing device to which the present technology is applied.

FIG. 2 is a flowchart for illustrating noise reduction processingexecuted by the image processing device.

FIG. 3 is a view illustrating an example of a filter used for reducingan image and NR.

FIG. 4 is a graph illustrating an example of luminance distribution of areduced image.

FIG. 5 is a graph illustrating an example of luminance distribution of anoise component extracted from the reduced image.

FIG. 6 is a graph illustrating an example of luminance distribution ofeach enlarged noise component.

FIG. 7 is a graph illustrating an example of luminance distribution ofan original image, a noise component, and an output image.

FIG. 8 is a view illustrating an example of a position in which a memoryis used in the image processing device to which the present technologyis applied.

FIG. 9 is a block diagram illustrating a first configuration example ofanother image processing device.

FIG. 10 is a block diagram illustrating a second configuration exampleof another image processing device.

FIG. 11 is a block diagram illustrating a third configuration example ofanother image processing device.

FIG. 12 is a block diagram illustrating an example of function sharingin a case where the image processing device to which the presenttechnology is applied is configured by hardware.

FIG. 13 is a block diagram illustrating a configuration example of acomputer.

MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the present technology (hereinafter, referred toas an embodiment) is hereinafter described. Meanwhile, the descriptionis given in the following order.

-   1. Embodiment-   2. Comparison with Other Noise Reducing Method-   3. Variation

<1. Embodiment> {Configuration Example of Information Processing Device100}

FIG. 1 illustrates an embodiment of an image processing device 100 towhich the present technology is applied.

The image processing device 100 is a device which outputs an image afterreducing noise of an original image which is an externally input image.The image processing device 100 is provided with an input unit 101, anoise reduction (NR) 102, a reduced image generation unit 103, a noiseextraction unit 104, a noise synthesis unit 105, a subtraction unit 106,and an output unit 107. The reduced image generation unit 103 isprovided with reduction units 121 a to 121 c. The noise extraction unit104 is provided with extraction units 131 a to 131 c. The noisesynthesis unit 105 is provided with enlarging units 151 a to 151 c andaddition units 152 a and 152 c.

The input unit 101 supplies the externally input original image to theNR 102 and the reduction unit 121 a of the reduced image generation unit103.

The NR 102 reduces a noise component in a predetermined frequency bandof the original image (hereinafter referred to as a first noisecomponent) and supplies the original image after the noise reduction tothe subtraction unit 106.

The reduced image generation unit 103 reduces the original image in astepwise manner and generates a plurality of reduced images.

Specifically, the reduction unit 121 a reduces the original image at apredetermined magnification and supplies a reduced image (hereinafterreferred to as a first reduced image) to the reduction unit 121 b andthe extraction unit 131 a.

The reduction unit 121 b reduces the first reduced image at apredetermined magnification and supplies a reduced image (hereinafterreferred to as a second reduced image) to the reduction unit 121 c andthe extraction unit 131 b.

The reduction unit 121 c reduces the second reduced image at apredetermined magnification and supplies a reduced image (hereinafterreferred to as a third reduced image) to the extraction unit 131 c.

The noise extraction unit 104 extracts a noise component in apredetermined frequency band of each of the first to third reducedimages.

Specifically, the extraction unit 131 a is provided with a noisereduction (NR) 141 a and a subtraction unit 142 a. The NR 141 a reducesa noise component in a predetermined frequency band of the first reducedimage and supplies the first reduced image after the noise reduction tothe subtraction unit 142 a. The subtraction unit 142 a obtains adifference between the first reduced image before the noise reductionand the first reduced image after the noise reduction, therebyextracting the noise component in a predetermined frequency band of thefirst reduced image (hereinafter, referred to as a second noisecomponent). The subtraction unit 142 a supplies the extracted secondnoise component to the addition unit 152 a.

The extraction unit 131 b is provided with a noise reduction (NR) 141 band a subtraction unit 142 b. The NR 141 b reduces a noise component ina predetermined frequency band of the second reduced image and suppliesthe second reduced image after the noise reduction to the subtractionunit 142 b. The subtraction unit 142 b obtains a difference between thesecond reduced image before the noise reduction and the second reducedimage after the noise reduction, thereby extracting the noise componentin a predetermined frequency band of the second reduced image(hereinafter, referred to as a third noise component). The subtractionunit 142 b supplies the extracted third noise component to the additionunit 152 b.

The extraction unit 151 c is provided with a noise reduction (NR) 141 cand a subtraction unit 142 c. The NR 141 c reduces a noise component ina predetermined frequency band of the third reduced image and suppliesthe third reduced image after the noise reduction to the subtractionunit 142 c. The subtraction unit 142 c obtains a difference between thethird reduced image before the noise reduction and the third reducedimage after the noise reduction, thereby extracting the noise componentin a predetermined frequency band of the third reduced image(hereinafter, referred to as a fourth noise component). The subtractionunit 142 c supplies the extracted fourth noise component to theenlarging unit 151 c.

The noise synthesis unit 105 synthesizes the second to fourth noisecomponents extracted from the first to third reduced images,respectively.

Specifically, the enlarging unit 151 c enlarges the fourth noisecomponent by up-sampling the same at a magnification opposite to that ofthe reduction unit 121 c forming a pair with the enlarging unit 151 cand supplies the enlarged fourth noise component to the addition unit152 b.

The addition unit 152 b adds the third noise component to the enlargedfourth noise component and supplies a noise component after addition(hereinafter referred to as a second synthesized noise component) to theenlarging unit 151 b.

The enlarging unit 151 b enlarges the second synthesized noise componentby up-sampling the same at a magnification opposite to that of thereduction unit 121 b forming a pair with the enlarging unit 151 b andsupplies the enlarged second synthesized noise component to the additionunit 152 a.

The addition unit 152 a adds the second noise component to the secondsynthesized noise component and supplies a noise component afteraddition (hereinafter referred to as a first synthesized noisecomponent) to the enlarging unit 151 a.

The enlarging unit 151 a enlarges the first synthesized noise componentby up-sampling the same at a magnification opposite to that of thereduction unit 121 a forming a pair with the enlarging unit 151 a andsupplies the enlarged first synthesized noise component to thesubtraction unit 106.

The subtraction unit 106 subtracts the first synthesized noise componentfrom the original image after the noise reduction and supplies theobtained image to the output unit 107.

The output unit 107 outputs the image supplied from the subtraction unit106 as an output image.

{Noise Reduction Processing}

Next, noise reduction processing executed by the image processing device100 is described with reference to a flowchart in FIG. 2. Meanwhile,this processing starts, for example, when the original image from whichthe noise component is to be reduced is input to the input unit 101.

At step S1, the reduced image generation unit 103 reduces the image in astepwise manner. Specifically, the input unit 101 supplies the originalimage to the NR 102 and the reduction unit 121 a.

For example, the reduction unit 121 a reduces the original image to halfin longitudinal and lateral directions to generate the first reducedimage. At that time, the reduction unit 121 a limits a frequency band ofthe first reduced image, for example, by using a reduction filter 201 aillustrated in FIG. 3. Specifically, the reduction filter 201 a is alow-pass filter which reduces the frequency band of the image to half.Therefore, supposing that a sampling frequency of the original image isfs and a maximum frequency of the original image is ½ fs, a maximumfrequency of the first reduced image is limited to ¼ fs.

The reduction unit 121 a supplies the generated first reduced image tothe reduction unit 121 b, the NR 141 a, and the subtraction unit 142 a.

For example, the reduction unit 121 b reduces the first reduced image tohalf in longitudinal and lateral directions to generate the secondreduced image. At that time, the reduction unit 121 b limits a frequencyband of the second reduced image, for example, by using a reductionfilter 201 b illustrated in FIG. 3. Specifically, the reduction filter201 b is the same low-pass filter as the reduction filter 201 a, and amaximum frequency of the second reduced image is limited to ⅛ fs.

The reduction unit 121 b supplies the generated second reduced image tothe reduction unit 121 c, the NR 141 b, and the subtraction unit 142 b.

For example, the reduction unit 121 c reduces the second reduced imageto half in longitudinal and lateral directions to generate the thirdreduced image. At that time, the reduction unit 121 c limits a frequencyband of the third reduced image, for example, by using a reductionfilter 201 c illustrated in FIG. 3. Specifically, the reduction filter201 c is the same low-pass filter as the reduction filters 201 a and 201b, and a maximum frequency of the third reduced image is limited to 1/16fs.

The reduction unit 121 c supplies the generated third reduced image tothe NR 141 c and the subtraction unit 142 c.

Graphs 212 a to 212 c in FIG. 4 illustrate examples of luminancedistribution of the first reduced image, the second reduced image, andthe third reduced image corresponding to the same position in theoriginal image 211. The position in the image is plotted along theabscissa and the luminance is plotted along the ordinate in the graphs212 a to 212 c.

As illustrated in the graphs 212 a to 212 c, a high-frequency componentis removed as the image is reduced.

At step S2, the image processing device 100 reduces and extracts thenoise component.

Specifically, for example, the NR 102 reduces the noise component in apredetermined frequency band of the original image (the first noisecomponent) by using a noise filter 202 a in FIG. 3 and supplies theoriginal image after the noise reduction to the subtraction unit 106. Inthis example, the same filter as the reduction filter 201 a used forreducing the original image is used as the noise filter 202 a andhigh-frequency noise of the original image is reduced.

For example, the NR 141 a reduces the noise component in a predeterminedfrequency band of the first reduced image by using a noise filter 202 bin FIG. 3 and supplies the first reduced image after the noise reductionto the subtraction unit 142 a. In this example, the same filter as thereduction filter 201 b used for reducing the first reduced image is usedas the noise filter 202 b and high-frequency noise of the first reducedimage is reduced.

The subtraction unit 142 a obtains a difference between the firstreduced image before the noise reduction and the first reduced imageafter the noise reduction, thereby extracting the noise component of thefirst reduced image (the second noise component). The subtraction unit142 a supplies the extracted second noise component to the addition unit152 a.

For example, the NR 141 b reduces the noise component in a predeterminedfrequency band of the second reduced image by using a noise filter 202 cin FIG. 3 and supplies the second reduced image after the noisereduction to the subtraction unit 142 b. In this example, the samefilter as the reduction filter 201 c used for reducing the secondreduced image is used as the noise filter 202 c and high-frequency noiseof the second reduced image is reduced.

The subtraction unit 142 b obtains a difference between the secondreduced image before the noise reduction and the second reduced imageafter the noise reduction, thereby extracting the noise component of thesecond reduced image (the third noise component). The subtraction unit142 b supplies the extracted third noise component to the addition unit152 b.

For example, the NR 141 c reduces the noise component in a predeterminedfrequency band of the third reduced image by using a noise filter 202 din FIG. 3 and supplies the third reduced image after the noise reductionto the subtraction unit 142 c. In this example, the same filter as thenoise filters 202 a to 202 c is used as the noise filter 202 c andhigh-frequency noise of the third reduced image is reduced.

The subtraction unit 142 c obtains a difference between the thirdreduced image before the noise reduction and the third reduced imageafter the noise reduction, thereby extracting the noise component of thethird reduced image (the fourth noise component). The subtraction unit142 c supplies the extracted fourth noise component to the enlargingunit 152 c.

In this manner, the extraction units 131 a to 131 c individually extractthe noise components of the first to third reduced images, respectively.

Also, the NR 102 and the extraction units 131 a to 131 c independentlyperform processing in parallel. In further detail, the NR 102 and theNRs 141 a to 141 c independently perform noise reduction processing inparallel.

A graph in the center in FIG. 3 schematically illustrates a relationshipbetween the frequency bands of the original image and the first to thirdreduced images and the frequency bands of the first noise component tothe fourth noise component. A square frame of the graph at the topindicates the frequency band of the original image and a hatched areaindicates the frequency band of the first noise component. A squareframe of the second graph indicates the frequency band of the firstreduced image and a hatched area indicates the frequency band of thesecond noise component. A square frame of the third graph indicates thefrequency band of the second reduced image and a hatched area indicatesthe frequency band of the third noise component. A square frame of thefourth graph indicates the frequency band of the third reduced image anda hatched area indicates the frequency band of the fourth noisecomponent.

Herein, the reduction filter 201 a applied to the original image and thenoise filter 202 a are made the same, the reduction filter 201 b appliedto the first reduced image and the noise filter 202 b are made the same,the reduction filter 201 c applied to the second reduced image and thenoise filter 202 c are made the same, so that the frequency bands of thefirst noise component, the second noise component, the third noisecomponent, and the fourth noise component are orthogonal to one anotherand do not overlap with one another. For example, the frequency band ofthe first noise component ranges from ¼ fs to ½ fs. The frequency bandof the second noise component ranges from ⅛ fs to ¼ fs. The frequencyband of the third noise component ranges from 1/16 fs to ⅛ fs. Thefrequency band of the fourth noise component is in a range not higherthan 1/16 fs. This prevents occurrence of overcorrection in which thenoise components are redundantly reduced.

Dotted waveforms in graphs 221 a to 221 c in FIG. 5 indicate examples ofluminance distribution of the noise components extracted from the firstreduced image, the second reduced image, and the third reduced image inthe example described above with reference to FIG. 4. The position inthe image is plotted along the abscissa and the luminance is plottedalong the ordinate in the graphs 221 a to 221 c. Also, the dottedwaveform in the graph 221 a indicates the luminance distribution of thesecond noise component, the dotted waveform in the graph 221 b indicatesthe luminance distribution of the third noise component, and the dottedwaveform in the graph 221 c indicates the luminance distribution of thefourth noise component. Meanwhile, solid waveforms in the graphs 221 ato 221 c indicates the luminance distributions of the respective reducedimages and are the same as the waveforms of the graphs 212 a to 212 c inFIG. 4.

At step S3, the noise synthesis unit 105 synthesizes the extracted noisecomponents.

Specifically, the enlarging unit 151 c enlarges the fourth noisecomponent by up-sampling the same at the magnification opposite to thatof the reduction unit 121 c and converts the fourth noise component tothe noise component in the frequency band in the second reduced image.The frequency band of the enlarged fourth noise component becomes afrequency band lower than that of the third noise component extractedfrom the second reduced image and do not overlap with the frequency bandof the third noise component. The enlarging unit 151 c supplies theenlarged fourth noise component to the addition unit 152 b.

The addition unit 152 b adds the third noise component to the enlargedfourth noise component and supplies the noise component after addition(the second synthesized noise component) to the enlarging unit 151 b.

The enlarging unit 151 b enlarges the second synthesized noise componentby up-sampling the same at the magnification opposite to that of thereduction unit 121 b and converts the second synthesized noise componentto the noise component in the frequency band in the first reduced image.The frequency band of the enlarged second synthesized noise componentbecomes a frequency band lower than that of the second noise componentextracted from the first reduced image and do not overlap with thefrequency band of the second noise component. The enlarging unit 151 bsupplies the enlarged second synthesized noise component to the additionunit 152 b.

The addition unit 152 a adds the second noise component to the enlargedsecond synthesized noise component and supplies the noise componentafter addition (the first synthesized noise component) to the enlargingunit 151 a.

The enlarging unit 151 a enlarges the first synthesized noise componentby up-sampling the same at the magnification opposite to that of thereduction unit 121 a and converts the first synthesized noise componentto the noise component in the frequency band in the original image. Thefrequency band of the enlarged first synthesized noise component becomesa frequency band lower than that of the first noise component extractedfrom the original image and do not overlap with the frequency band ofthe first noise component. The enlarging unit 151 a supplies theenlarged first synthesized noise component to the subtraction unit 106.

In this manner, the noise synthesis unit 105 adds the noise component inorder from the noise component of the smallest third reduced image whileup-sampling the same at an enlargement factor opposite to a reductionfactor when reducing the corresponding reduced image, therebysynthesizing the noise components. That is, the fourth noise componentextracted from the third reduced image is up-sampled at the enlargementfactor opposite to the reduction factor when reducing the third reducedimage and is added to the third noise component extracted from thesecond reduced image. Also, the second synthesized noise componentobtained by adding the third noise component to the fourth noisecomponent is up-sampled at the enlargement factor opposite to thereduction factor when reducing the second reduced image and is added tothe second noise component extracted from the first reduced image.

Graphs 231 a to 231 c in FIG. 6 illustrate examples of luminancedistribution of each enlarged noise component. The position in the imageis plotted along the abscissa and the luminance is plotted along theordinate in the graphs 231 a to 231 c. Specifically, the graph 231 cillustrates the example of the luminance distribution in a case wherethe fourth noise component is enlarged to the noise component in thefrequency band in the original image. The graph 231 b illustrates theexample of the luminance distribution in a case where the secondsynthesized noise component is enlarged to the noise component in thefrequency band in the original image. The graph 231 a illustrates theexample of the luminance distribution in a case where the firstsynthesized noise component is enlarged to the noise component in thefrequency band in the original image.

As illustrated in the example in FIG. 6, in the noise synthesis unit105, the noise components in the respective frequency bands extractedfrom the extraction units 131 a to 131 c are synthesized while beingpropagated.

At step S4, the subtraction unit 106 removes the synthesized noisecomponent. That is, the subtraction unit 106 removes the firstsynthesized noise component from the original image by obtaining adifference between the original image from which the noise component isreduced by the NR 102 and the first synthesized noise component. Thesubtraction unit 106 supplies the original image from which the firstsynthesized noise component is removed to the output unit 107. Theoutput unit 107 outputs the supplied image as the output image to asubsequent device.

Graphs 241 to 243 in FIG. 7 illustrate examples of luminancedistribution of the original image, the noise component, and the outputimage. The position in the image is plotted along the abscissa and theluminance is plotted along the ordinate in the graphs 241 to 243.Specifically, the graph 241 illustrates the example of the luminancedistribution of the original image after the noise is reduced by the NR102. The graph 242 illustrates the example of the luminance distributionof the first synthesized noise component. The graph 243 illustrates theexample of the luminance distribution of the output image obtained afterthe first synthesized noise component illustrated in the graph 242 isremoved from the original image illustrated in the graph 241.

Thereafter, the noise reduction processing is finished.

<2. Comparison with Other Noise Reducing Method>

Herein, with reference to FIGS. 8 to 11, the noise reducing method bythe image processing device 100 is compared with another noise reducingmethod.

{Memory Used in Image Processing Device 100}

FIG. 8 illustrates an example of a position in which a memory is used inthe image processing device 100.

Specifically, in a position Al before the NR 102 and the reduction unit121 a, a memory is used for an original image.

Also, in a position B1 before the reduction unit 121 b and the NR 141 a,a memory is used for the first reduced image. In a position B2 beforethe enlarging unit 151 a, a memory is used for the first synthesizednoise component having the same resolution as that of the first reducedimage.

Furthermore, in a position C1 before the reduction unit 121 c and the NR141 b, a memory is used for the second reduced image. In a position C2before the enlarging unit 151 b, a memory is used for the secondsynthesized noise component having the same resolution as that of thesecond reduced image.

Also, in a position D1 before the NR 141 c, a memory is used for thethird reduced image. In a position C2 before the enlarging unit 151 c, amemory is used for the fourth noise component having the same resolutionas that of the third reduced image.

{Comparison with Image Processing Device 300}

FIG. 9 illustrates a configuration example of an image processing device300. The image processing device 300 is provided with an input unit 301,bypass filters (BPFs) 302 a to 302 c, noise reductions (NRs) 303 a to303 d, enlarging units 304 a to 304 c, addition units 305 a to 305 c,and an output unit 306. The BPF 302 a is provided with a reduction unit311 a, an enlarging unit 312 a, and a subtraction unit 313 a. The BPF302 b is provided with a reduction unit 311 b, an enlarging unit 312 b,and a subtraction unit 313 b. The BPF 302 c is provided with a reductionunit 311 c, an enlarging unit 312 c, and a subtraction unit 313 c.

The input unit 301 supplies an input original image to the reductionunit 311 a and the subtraction unit 313 a.

The reduction unit 311 a reduces the original image at the samemagnification as that of the reduction unit 121 a of the imageprocessing device 100 in FIG. 1. The reduction unit 311 a supplies areduced image (hereinafter referred to as a first reduced image) to thereduction unit 311 b, the enlarging unit 312 a, and the subtraction unit313 b.

The enlarging unit 312 a enlarges the first reduced image at amagnification opposite to that of the reduction unit 311 a and suppliesthe enlarged first reduced image to the subtraction unit 313 a.

The subtraction unit 313 a obtains a difference between the originalimage and the enlarged first reduced image and supplies an obtainedimage (hereinafter referred to as a high-frequency original image) tothe NR 303 a. The high-frequency original image is an image obtained byextracting a high-frequency component in a predetermined band from theoriginal image.

The reduction unit 311 b reduces the first reduced image at the samemagnification as that of the reduction unit 121 b of the imageprocessing device 100 in FIG. 1. The reduction unit 311 b supplies areduced image (hereinafter referred to as a second reduced image) to thereduction unit 311 c, the enlarging unit 312 b, and the subtraction unit313 c.

The enlarging unit 312 b enlarges the second reduced image at amagnification opposite to that of the reduction unit 311 b and suppliesthe enlarged second reduced image to the subtraction unit 313 b.

The subtraction unit 313 b obtains a difference between the firstreduced image and the enlarged second reduced image and supplies anobtained image (hereinafter referred to as a first high-frequencyreduced image) to the NR 303 b. The first high-frequency reduced imageis an image obtained by extracting a high-frequency component in apredetermined band from the first reduced image.

The reduction unit 311 c reduces the original image at the samemagnification as that of the reduction unit 121 c of the imageprocessing device 100 in FIG. 1. The reduction unit 311 c supplies areduced image (hereinafter referred to as a third reduced image) to theenlarging unit 312 c and the NR 303 d.

The enlarging unit 312 c enlarges the third reduced image at amagnification opposite to that of the reduction unit 311 c and suppliesthe enlarged third reduced image to the subtraction unit 313 c.

The subtraction unit 313 c obtains a difference between the secondreduced image and the enlarged third reduced image and supplies anobtained image (hereinafter referred to as a second high-frequencyreduced image) to the NR 303 c. The second high-frequency reduced imageis an image obtained by extracting a high-frequency component in apredetermined band from the second reduced image.

The NR 303 a reduces a noise component of the high-frequency originalimage and supplies the high-frequency original image after the noisereduction to the addition unit 305 b.

The NR 303 b reduces a noise component of the first high-frequencyreduced image and supplies the first high-frequency reduced image afterthe noise reduction to the addition unit 305 b.

The NR 303 c reduces a noise component of the second high-frequencyreduced image and supplies the second high-frequency reduced image afterthe noise reduction to the addition unit 305 c.

The NR 303 d reduces a noise component of the third reduced image andsupplies the third reduced image after the noise reduction to theenlarging unit 304 c.

Therefore, the NRs 303 a to 303 d reduce the noise components indifferent frequency bands of the original image, respectively.

The enlarging unit 304 c enlarges the third reduced image after thenoise reduction at a magnification opposite to that of the reductionunit 311 c and supplies the enlarged third reduced image to the additionunit 305 c.

The addition unit 305 c adds the second high-frequency reduced imageafter the noise reduction to the enlarged third reduced image andsupplies the image after addition (hereinafter referred to as a secondsynthesized image) to the enlarging unit 304 b.

The enlarging unit 304 b enlarges the second synthesized image at amagnification opposite to that of the reduction unit 311 b and suppliesthe enlarged second synthesized image to the addition unit 305 b.

The addition unit 305 b adds the second high-frequency reduced imageafter the noise reduction to the enlarged second synthesized image andsupplies an image after addition (hereinafter referred to as a firstsynthesized image) to the enlarging unit 304 a.

The enlarging unit 304 a enlarges the first synthesized image at amagnification opposite to that of the reduction unit 311 a and suppliesthe enlarged first synthesized image to the addition unit 305 a.

The addition unit 305 a adds the high-frequency original image after thenoise reduction to the enlarged first synthesized image and supplies animage after addition to the output unit 306.

The output unit 306 outputs the image supplied from the addition unit305 a as an output image.

In the image processing device 300, in a position A1 before thereduction unit 311 a, a memory is used for the original image. In aposition A2 before the NR 303 a, a memory is used for the high-frequencyoriginal image having the same resolution as that of the original image.

Also, in a position B1 before the reduction unit 311 b and the enlargingunit 312 a, a memory is used for the first reduced image. In a positionB2 before the NR 303 b, a memory is used for the first high-frequencyreduced image having the same resolution as that of the first reducedimage. In a position B3 before the enlarging unit 304 a, a memory isused for the first synthesized image having the same resolution as thatof the first reduced image.

Furthermore, in a position C1 before the reduction unit 311 c and theenlarging unit 312 b, a memory is used for the second reduced image. Ina position C2 before the NR 303 c, a memory is used for the secondhigh-frequency reduced image having the same resolution as that of thesecond reduced image. In a position C3 before the enlarging unit 304 b,a memory is used for the second synthesized image having the sameresolution as that of the second reduced image.

Also, memories are used for the third reduced image in a position D1before the enlarging unit 312 c and the NR 303 d and a position D2before the enlarging unit 304 c.

Comparing FIG. 8 with FIG. 9, the image processing device 100 uses asmaller memory amount than the image processing device 300. Also, in theimage processing device 100, the BPF is not used unlike in the imageprocessing device 300. Therefore, the image processing device 100 mayreduce a circuit scale and an arithmetic amount as compared with theimage processing device 300.

Also, in the image processing device 300, the NRs 303 a to 303 cindependently reduce the noise components in the respective frequencybands extracted by the BPFs 302 a to 302 c. Therefore, in the NRs 303 ato 303 c, only AC components are subject to the noise reduction, so thatperformance of the noise reduction processing becomes unstable. Also, inthe image processing device 300, a noise reduction effect depends onperformance of the BPFs 302 a to 302 c. However, since it is difficultto completely separate pass bands of the BPFs 302 a to 302 c, forexample, a frequency band in which noise is redundantly reduced isgenerated, and the noise reduction effect is deteriorated due toovercorrection.

On the other hand, in the image processing device 100, the BPF is notused as described above. Also, the NR 102 performs the noise reductionof the original image, and the NRs 141 a to 141 c perform the noisereduction of the reduced image. Therefore, noise reduction targets ofthe NR 102 and the NRs 141 a to 141 c are DC components and the ACcomponents, so that performance of the NR 102 and the NRs 141 a to 141 cis stabilized.

As described above, the image processing device 100 is excellent innoise reduction effect as compared to the image processing device 300and may decrease the circuit scale and the arithmetic amount.

{Comparison with Image Processing Device 400}

FIG. 10 illustrates a configuration example of an image processingdevice 400. Meanwhile, in the drawing, a portion corresponding to thatin FIG. 9 is assigned with the same reference sign.

The image processing device 400 differs from the image processing device300 in FIG. 9 in positions of the NRs 303 a to 303 c and the additionunits 305 a to 305 c.

Out of the processing of the image processing device 400, the processingdifferent from that of the image processing device 300 is hereinespecially described.

The BPF 302 a generates the high-frequency original image and the firstreduced image as described above. The BPF 302 a supplies thehigh-frequency original image to the addition unit 305 a and suppliesthe first reduced image to the reduction unit 311 b and the subtractionunit 313 b.

The BPF 302 b generates the first high-frequency reduced image and thesecond reduced image as described above. The BPF 302 b supplies thefirst high-frequency reduced image to the addition unit 305 b andsupplies the second reduced image to the reduction unit 311 c and thesubtraction unit 313 c.

The BPF 302 c generates the second high-frequency reduced image and thethird reduced image as described above. The BPF 302 c supplies thesecond high-frequency reduced image to the addition unit 305 c andsupplies the third reduced image to the NR 303 d.

The NR 303 d reduces a noise component of the third reduced image andsupplies the third reduced image after the noise reduction to theenlarging unit 304 c.

The enlarging unit 304 c enlarges the third reduced image after thenoise reduction at a magnification opposite to that of the reductionunit 311 c and supplies the enlarged third reduced image to the additionunit 305 c.

The addition unit 305 c adds the second high-frequency reduced image tothe enlarged third reduced image and supplies an image after addition(hereinafter referred to as a third synthesized image) to the NR 303 c.Meanwhile, the third synthesized image is the same as the secondsynthesized image in the image processing device 300 in FIG. 9.

The NR 303 c reduces a noise component of the third synthesized imageand supplies the third synthesized image after the noise reduction tothe enlarging unit 304 b.

The enlarging unit 304 b enlarges the third synthesized image at themagnification opposite to that of the reduction unit 311 b and suppliesthe enlarged third synthesized image to the addition unit 305 b.

The addition unit 305 b adds the first high-frequency reduced image tothe third synthesized image and supplies an image after addition(hereinafter referred to as a second synthesized image) to the NR 303 b.

The NR 303 b reduces a noise component of the second synthesized imageand supplies the second synthesized image after the noise reduction tothe enlarging unit 304 a.

The enlarging unit 304 a enlarges the second synthesized image at themagnification opposite to that of the reduction unit 311 a and suppliesthe enlarged second synthesized image to the addition unit 305 a.

The addition unit 305 a adds the high-frequency original image to theenlarged second synthesized image and supplies the image after addition(hereinafter referred to as a first synthesized image) to the NR 303 a.

The NR 303 a reduces a noise component of the first synthesized imageand supplies the first synthesized image after the noise reduction tothe output unit 306.

The output unit 306 outputs the first synthetic image after the noisereduction as the output image to the subsequent device.

In the image processing device 400, a memory is used for the originalimage in a position A1 before the reduction unit 311 a. In a position A2before the NR 303 a, a memory is used for the first synthesized imagehaving the same resolution as that of the original image.

Also, in a position B1 before the reduction unit 311 b and the enlargingunit 312 a, a memory is used for the first reduced image. The memoriesare used for the second synthesized image having the same resolution asthat of the first reduced image in a position B2 before the NR 303 b anda position B3 before the enlarging unit 304 a.

Furthermore, in a position C1 before the reduction unit 311 c and theenlarging unit 312 b, a memory is used for the second reduced image.Memories are used for the third synthesized image having the sameresolution as that of the second reduced image in a position C2 beforethe NR 303 c and a position C3 before the enlarging unit 304 b.

Also, memories are used for the third reduced image in a position D1before the enlarging unit 312 c and the NR 303 d and a position D2before the enlarging unit 304 c.

Comparing FIG. 8 with FIG. 10, the image processing device 100 uses asmaller memory amount than the image processing device 400. In the imageprocessing device 100, the BPF is not used unlike in the imageprocessing device 400. Therefore, the image processing device 100 mayreduce the circuit scale and the arithmetic amount as compared with theimage processing device 400.

Also, in the image processing device 400, as in the image processingdevice 300, the noise reduction effect depends on the performance of theBPFs 302 a to 302 c, and as a result, the noise reduction effect isdeteriorated. On the other hand, since the BPF is not used in the imageprocessing device 100, the noise reduction effect is not deteriorated.

Furthermore, in the image processing device 400, as in the imageprocessing device 300, the noise reduction effect depends on theperformance of the BPFs 302 a to 302 c, so that the noise reductioneffect is deteriorated.

Also, in the image processing device 400, the NRs 303 a to 303 dsequentially perform processing. That is, the NR 303 c performs theprocessing after the processing of the NR 303 d finishes, the NR 303 bperforms the processing after the processing of the NR 303 c finishes,and the NR 303 a performs the processing after the processing of the NR303 b finishes. Therefore, the stand-by time for the processing becomeslonger, and the used amount of the memory further increases.

On the other hand, in the image processing device 100, as describedabove, the NR 102 and the NRs 141 a to 141 c independently perform theprocessing in parallel, so that it is possible to shorten the stand-bytime and reduce the used amount of the memory.

As described above, the image processing device 100 is excellent innoise reduction effect as compared to the image processing device 400,and may increase a processing speed and decrease the circuit scale andthe arithmetic amount.

{Comparison with Image Processing Device 500}

FIG. 11 illustrates a configuration example of an image processingdevice 500. Meanwhile, the image processing device 500 is modeled afterthe image processing device disclosed in Patent Document 1 describedabove.

The image processing device 500 is provided with an input unit 501,reduction units 502 a to 502 c, noise reductions (NRs) 503 a to 503 c,subtraction units 504 a to 504 c, addition units 505 a and 505 b,enlarging units 506 a to 506 c, subtraction units 507 a to 507 c, anoise reduction (NR) 508, and an output unit 509.

The input unit 501 supplies an input original image to the reductionunit 502 a and the subtraction unit 507 a.

The reduction unit 502 a reduces the original image at the samemagnification as that of the reduction unit 121 a of the imageprocessing device 100 in FIG. 1. The reduction unit 502 a supplies areduced image (hereinafter referred to as a first reduced image) to thereduction unit 502 b and the subtraction unit 507 b.

The reduction unit 502 b reduces the first reduced image at the samemagnification as that of the reduction unit 121 b of the imageprocessing device 100 in FIG. 1. The reduction unit 502 b supplies areduced image (hereinafter referred to as a second reduced image) to thereduction unit 502 c and the subtraction unit 507 c.

The reduction unit 502 c reduces the original image at the samemagnification as that of the reduction unit 121 c of the imageprocessing device 100 in FIG. 1. The reduction unit 502 c supplies areduced image (hereinafter referred to as a third reduced image) to theNR 503 c and the subtraction unit 504 c.

The NR 503 c reduces a noise component of the third reduced image andsupplies the third reduced image after the noise reduction to thesubtraction unit 504 c.

The subtraction unit 504 c obtains a difference between the thirdreduced image before the noise reduction and the third reduced imageafter the noise reduction, thereby extracting the noise component of thethird reduced image (hereinafter referred to as a third noisecomponent). The subtraction unit 504 c supplies the extracted thirdnoise component to the enlarging unit 506 c.

The enlarging unit 506 c enlarges the third noise component byup-sampling the same at a magnification opposite to that of thereduction unit 502 c and converts the third noise component to a noisecomponent in a frequency band in the second reduced image. The enlargingunit 506 c supplies the enlarged third noise component to thesubtraction unit 507 c and the addition unit 505 b.

The subtraction unit 507 c obtains a difference between the secondreduced image and the enlarged third noise component, thereby removingthe third noise component from the second reduced image. The subtractionunit 507 c supplies the second reduced image after the noise removal tothe NR 503 b and the subtraction unit 504 b.

The NR 503 b reduces a noise component of the second reduced image andsupplies the second reduced image after the noise reduction to thesubtraction unit 504 b.

The subtraction unit 504 b obtains a difference between the secondreduced image before the noise reduction and the second reduced imageafter the noise reduction, thereby extracting the noise component of thesecond reduced image after the removal of the third noise component(hereinafter, referred to as a second noise component). The subtractionunit 504 b supplies the extracted second noise component to the additionunit 505 b.

The addition unit 505 b adds the second noise component to the enlargedthird noise component and supplies a noise component after addition(hereinafter referred to as a second synthesized noise component) to theenlarging unit 506 b.

The enlarging unit 506 b enlarges the second synthesized noise componentby up-sampling the same at a magnification opposite to that of thereduction unit 502 b and converts the second synthesized noise componentto a noise component in a frequency band in the first reduced image. Theenlarging unit 506 b supplies the enlarged second synthesized noisecomponent to the subtraction unit 507 b and the addition unit 505 a.

The subtraction unit 507 c obtains a difference between the firstreduced image and the enlarged second synthesized noise component,thereby removing the second synthesized noise component from the firstreduced image. The subtraction unit 507 b supplies the first reducedimage after the noise removal to the NR 503 a and the subtraction unit504 a.

The NR 503 a reduces a noise component of the first reduced image andsupplies the first reduced image after the noise reduction to thesubtraction unit 504 a.

The subtraction unit 504 b obtains a difference between the firstreduced image before the noise reduction and the first reduced imageafter the noise reduction, thereby extracting the noise component of thefirst reduced image after the removal of the second synthesized noisecomponent (hereinafter, referred to as a first noise component). Thesubtraction unit 504 a supplies the extracted first noise component tothe addition unit 505 a.

The addition unit 505 a adds the first noise component to the enlargedsecond synthesized noise component and supplies a noise component afteraddition (hereinafter referred to as a first synthesized noisecomponent) to the enlarging unit 506 a.

The enlarging unit 506 a enlarges the first synthesized noise componentby up-sampling the same at a magnification opposite to that of thereduction unit 121 a, thereby converting the first synthesized noisecomponent to a noise component in a frequency band in the originalimage. The enlarging unit 506 a supplies the enlarged first synthesizednoise component to the subtraction unit 507 a.

The subtraction unit 507 a obtains a difference between the originalimage and the enlarged first synthesized noise component, therebyremoving the first synthesized noise component from the original image.The subtraction unit 507 a supplies the original image after the noiseremoval to the NR 508.

The NR 508 reduces a noise of the original image after the removal ofthe first synthesized noise component and supplies the original imageafter the noise reduction to the output unit 509.

The output unit 509 outputs the original image after the noise reductionas the output image.

As described above, the image processing device 500 propagates theextracted noise component in each frequency band as in the imageprocessing device 100, but this is greatly different from the imageprocessing device 100 in that the NRs 503 a to 503 c and the NR 508sequentially perform the processing. Therefore, a used amount of thememory increases.

Specifically, in the image processing device 500, a memory is used forthe original image in a position A1 before the reduction unit 502 a anda position A2 before the NR 508.

Also, memories are used for the first reduced image in a position B1before the reduction unit 502 b and a position B2 before the NR 503 a.In a position B3 before the enlarging unit 506 a, a memory is used forthe first synthesized noise component having the same resolution as thatof the first reduced image.

Furthermore, memories are used for the second reduced image in aposition C1 before the reduction unit 502 c and a position C2 before theNR 503 b. In a position C3 before the enlarging unit 506 b, a memory isused for the second synthesized noise component having the sameresolution as that of the second reduced image.

Also, memories are used for the third reduced image in a position D1before the NR 503 c and a position D2 before the enlarging unit 506 c.

Comparing FIG. 8 with FIG. 11, the image processing device 100 uses asmaller memory amount than the image processing device 500. Therefore,the image processing device 100 may reduce the circuit scale as comparedwith the image processing device 500.

Also, in the image processing device 500, since the NRs 503 a to 503 cand the NR 508 sequentially perform processing, stand-by time for theprocessing becomes longer and the used amount of the memory furtherincreases.

As described above, the image processing device 100 may increase theprocessing speed and reduce the circuit scale as compared with the imageprocessing device 500. Also, the noise reduction effect of the imageprocessing device 100 and that of the image processing device 500 aresubstantially equivalent to each other.

<3. Variation>

Hereinafter, a variation of the above-described embodiment of thepresent technology is described.

In the description above, the example in which the reduction factors ofall the reduction units 121 a to 121 c are the same is described, butthey are not necessarily the same. Furthermore, in the abovedescription, the example in which the enlargement factors of all theenlarging units 151 a to 151 c are the same is described, but they arenot necessary the same. However, the reduction factor and theenlargement factor of the reduction unit and the enlarging unit forminga pair (for example, the reduction unit 121 a and the enlarging unit 151a) must be in a relationship of inverse numbers.

Also, although the example in which all the filters used by thereduction units 121 a to 121 c are the same is described above, they arenot necessarily the same. Similarly, the filters used by the enlargingunits 151 a to 151 c are not necessarily the same. Furthermore, in thedescription above, the example in which the filter for reducing and thefilter for NR applied to the same image are the same is described, butthey are not required to be the same. However, it is necessary to selectthe filter for reducing and the filter for NR so that the frequencybands reduced by the respective NRs decrease are orthogonal.

Also, although the example in which the image is reduced in three stepsand the noise component is extracted from each reduced image isdescribed in the description above, the number of steps for reducing theimage may be set to an arbitrary value not smaller than one.

Meanwhile, the present technology is applicable to various devices,systems, software and the like having a function of reducing the imagenoise.

{Configuration Example of Computer}

A series of processes described above may be executed by hardware or bysoftware.

FIG. 12 is a block diagram illustrating an example of function sharingin a case where the image processing device 100 is configured byhardware. An image processing device 600 in FIG. 12 is provided with aninput unit 601, a reduction/noise extraction unit 602, a storage unit603, a noise synthesis unit 604, a noise component subtraction unit 605,and an output unit 606.

The input unit 601 corresponds to the input unit 101 of the imageprocessing device 100. The reduction/noise extraction unit 602 includesthe reduced image generation unit 103 and a noise extraction unit 104 ofthe image processing device 100. The storage unit 603 is configured bySRAM and DRAM, for example, and is used for storing data in thepositions A1 to D2 in FIG. 8. The noise synthesis unit 604 correspondsto the noise synthesis unit 105 of the image processing device 100. Thenoise component subtraction unit 605 includes the NR 102 and thesubtraction unit 106 of the image processing device 100. The output unit606 corresponds to the output unit 606 of the image processing device100.

Also, in a case where a series of processes is performed by software, aprogram which configures the software is installed on a computer.Herein, the computer includes a computer built in dedicated hardware, ageneral-purpose personal computer, for example, capable of executingvarious functions by various programs installed and the like.

FIG. 13 is a block diagram illustrating a configuration example ofhardware of a computer 800 which executes the above-described series ofprocesses by a program.

In the computer 800, a central processing unit (CPU) 801, a read onlymemory (ROM) 802, and a random-access memory (RAM) 803 are connected toone another through a bus 804.

An input/output interface 805 is further connected to the bus 804. Aninput unit 806, an output unit 807, a storage unit 808, a communicationunit 809, and a drive 810 are connected to the input/output interface805.

The input unit 806 includes a keyboard, a mouse, a microphone and thelike. The output unit 807 includes a display, a speaker and the like.The storage unit 808 includes a hard disk, a non-volatile memory and thelike. The communication unit 809 includes a network interface and thelike. The drive 810 drives a removable medium 811 such as a magneticdisk, an optical disk, a magnetooptical disk, or a semiconductor memory.

In the computer 800 configured in the above-described manner, the CPU801 loads the program stored in the storage unit 808, for example, onthe RAM 803 through the input/output interface 805 and the bus 804 toexecute, so that a series of processes described above is performed.

The program executed by the computer 800 (CPU 801) may be recorded onthe removable medium 811 as a package medium and the like to beprovided, for example. Also, the program may be provided by means of awired or wireless transmission medium such as a local region network,the Internet, and digital broadcasting.

In the computer 800, the program may be installed on the storage unit808 through the input/output interface 805 by mounting the removablemedium 811 on the drive 810. Also, the program may be received by thecommunication unit 809 through the wired or wireless transmission mediumto be installed on the storage unit 808. In addition, the program may beinstalled in advance on the ROM 802 and the storage unit 808.

Meanwhile, the program executed by the computer 800 may be the programof which processes are performed in chronological order in the orderdescribed in this specification or may be the program of which processesare performed in parallel or at required timing such as when a call isissued.

Also, in this specification, a system is intended to mean assembly of aplurality of components (devices, modules (parts) and the like) and itdoes not matter whether all the components are in the same casing.Therefore, a plurality of devices stored in different casings connectedthrough the network and one device obtained by storing a plurality ofmodules in one casing are the systems.

Furthermore, the embodiments of the present technology are not limitedto the above-described embodiment and various modifications may be madewithout departing from the gist of the present technology.

For example, the present technology may be configured as cloud computingin which a function is shared by a plurality of devices through thenetwork to process together.

Also, each step described in the above-described flowchart may beexecuted by one device or executed by a plurality of devices in a sharedmanner.

Furthermore, in a case where a plurality of processes is included in onestep, a plurality of processes included in one step may be executed byone device or by a plurality of devices in a shared manner.

Also, the effect described in this specification is illustrative onlyand is not limitative; there may also be another effect.

Furthermore, the present technology may also have followingconfigurations, for example.

(1)

An image processing device provided with:

a reduced image generation unit which reduces an original image in astepwise manner to generate one or more n reduced images;

a noise reduction unit which reduces a noise component in apredetermined frequency band of the original image;

a noise extraction unit which performs processing of extracting a noisecomponent in a predetermined frequency band from each of the reducedimages in parallel;

a noise synthesis unit which synthesizes noise components extracted fromthe respective reduced images; and

a subtraction unit which subtracts a synthesized noise component fromthe original image after noise reduction.

(2)

The image processing device according to (1) described above,

in which frequency bands of the noise components extracted from therespective reduced images are not overlapped with a frequency band inwhich the noise component is reduced by the noise reduction unit and afrequency band of the noise component extracted from another reducedimage.

(3)

The image processing device according to (2) described above,

in which the noise reduction unit reduces the noise component of theoriginal image by using a filter the same as a filter used for reducingthe original image, and the noise extraction unit extracts the noisecomponent of each of the reduced images by using a filter the same as afilter used for reducing each of the reduced images.

(4)

The image processing device according to any one of (1) to (3) describedabove,

in which the noise extraction unit is provided with n extraction unitswhich individually extract the noise components of the respectivereduced images, and

the noise reduction unit and the n extraction units independentlyperform processing in parallel.

(5)

The image processing device according to any one of (1) to (4) describedabove,

in which the noise synthesis unit synthesizes the noise components byadding the noise components in order from the noise component of thesmallest reduced image while up-sampling at an enlargement factoropposite to a reduction factor when reducing the corresponding reducedimage in a case of n≥2.

(6)

An image processing method provided with:

a reduced image generating step of reducing an original image in astepwise manner to generate one or more n reduced images;

a noise reducing step of reducing a noise component in a predeterminedfrequency band of the original image;

a noise extracting step of performing processing of extracting a noisecomponent in a predetermined frequency band from each of the reducedimages in parallel;

a noise synthesizing step of synthesizing noise components extractedfrom the respective reduced images; and

a subtracting step of subtracting a synthesized noise component from theoriginal image after noise reduction.

REFERENCE SIGNS LIST

-   100 Image processing device-   102 Reduced image generation unit-   103 Noise extraction unit-   104 Noise synthesis unit-   105 Noise reduction-   106 Subtraction unit-   121 a to 121 c Reduction unit-   131 a to 131 c Extraction unit-   141 a to 141 c Noise reduction-   142 a to 142 c Subtraction unit-   151 a to 151 c Enlarging unit-   152 a, 152 b Addition unit-   600 Image processing device-   602 Reduction/noise extraction unit-   604 Noise synthesis unit-   605 Noise component subtraction unit

1. An image processing device comprising: a reduced image generationunit which reduces an original image in a stepwise manner to generateone or more n reduced images; a noise reduction unit which reduces anoise component in a predetermined frequency band of the original image;a noise extraction unit which performs processing of extracting a noisecomponent in a predetermined frequency band from each of the reducedimages in parallel; a noise synthesis unit which synthesizes noisecomponents extracted from the respective reduced images; and asubtraction unit which subtracts a synthesized noise component from theoriginal image after noise reduction.
 2. The image processing deviceaccording to claim 1, wherein frequency bands of the noise componentsextracted from the respective reduced images are not overlapped with afrequency band in which the noise component is reduced by the noisereduction unit and a frequency band of the noise component extractedfrom another reduced image.
 3. The image processing device according toclaim 2, wherein the noise reduction unit reduces the noise component ofthe original image by using a filter the same as a filter used forreducing the original image, and the noise extraction unit extracts thenoise component of each of the reduced images by using a filter the sameas a filter used for reducing each of the reduced images.
 4. The imageprocessing device according to claim 1, wherein the noise extractionunit is provided with n extraction units which individually extract thenoise components of the respective reduced images, and the noisereduction unit and the n extraction units independently performprocessing in parallel.
 5. The image processing device according toclaim 1, wherein the noise synthesis unit synthesizes the noisecomponents by adding the noise components in order from the noisecomponent of the smallest reduced image while up-sampling at anenlargement factor opposite to a reduction factor when reducing thecorresponding reduced image in a case of n≥2.
 6. An image processingmethod comprising: a reduced image generating step of reducing anoriginal image in a stepwise manner to generate one or more n reducedimages; a noise reducing step of reducing a noise component in apredetermined frequency band of the original image; a noise extractingstep of performing processing of extracting a noise component in apredetermined frequency band from each of the reduced images inparallel; a noise synthesizing step of synthesizing noise componentsextracted from the respective reduced images; and a subtracting step ofsubtracting a synthesized noise component from the original image afternoise reduction.